124 NEW YORK STATE MUSEUM 



present. This was called the Barton gneiss. It is obviously the 

 characteristic syenite of the Adirondack area as repeatedly described 

 in later years by Gushing, Smyth and the writer. The additional 

 study of the drill cores but serves to confirm its abundance in the 

 series. 



Lying below the Barton Hill ore body and between the Arch pit 

 and the Lovers pit, is a goodly exposure of typical basic gabbro, so 

 that there can be no doubt that this rock is represented in the hill 

 in an important way. Exposures are fragmentary because of the 

 ever present glacial drift, but the t3^pical and unmistakable gabbro 

 is succeeded as one follows along to the north, by a dark, basic 

 and at times garnetiferous gneiss, which one might naturally and 

 with great reason regard as a metamorphoseci form of the gabbro 

 itself. This was the view taken in 1898. Repeated and painstak- 

 ing study of the exposures since then, and due consideration of the 

 basic phases of the syenite series and of the character of the feld- 

 spars, which are largely orthoclase, have led to the conclusion that 

 this basic gneiss belongs rather with the syenites than with the gab- 

 bros, and that the gabbro as seen is a separate intrusive mass. Yet 

 it must be said that there are very puzzling things to be seen. Thus 

 as one follows along the foot wall of the ore above the Lovers pit 

 and toward the South pit, there are exposures of dark, gneissoid 

 rock, apparently basic syenite, yet with many little garnets like the 

 gabbro. Again beyond this point there is rock which is believed 

 to be true gabbro as mapped in 1898. Yet as to the shape of the 

 gabbro intrusive mass, no conclusion could be reached. It is in- 

 volved in the basic gneiss, and so poorly exposed because of drift, 

 that it is very easy to begin to speculate as to whether a mass of 

 absorbed limestone might not locally change a syenitic magma into 

 onq gabbroic in character. Practically the same relations, equally 

 puzzling in character, appear on the summit of the hill above the 

 Smith mine, where garnetiferous basic (syenite) gneisses are again 

 associated with gabbro in a very obscure manner. 



In the close observation of this hillside below the Lovers pit, the 

 writer also happened on what appeared to be a small dike, about 

 10 inches thick, striking with the schistosity of the basic syenitic 

 gneiss, but cutting it on the dip. It is a quite acidic rock, and re- 

 veals in the slide, quartz and orthoclase ' as the most abundant 

 minerals, less oligoclase, and a few shreds of dirty green horn- 

 blende, so molded around the other minerals as to suggest either 

 crushing and dragging or secondafy crystallization. There is a 



